1. Field of the Invention
The present invention relates generally to an apparatus and method for water purification using solar energy. More specifically, the present pertains to the desalination and purification of a water source using solar energy.
2. Description of the Related Art
Fresh water represents less than 3% of the water on earth. Of this 3%, nearly 75% is xe2x80x9ctrappedxe2x80x9d as ice throughout the world, predominantly on the polar ice caps. The remaining 97% of the earth""s water is in the form of salt water or brackish water. Pollutants and drought result in further limit the supply of fresh water in some locations.
As the world""s population increases, demand for fresh water has increased especially in arid and semi-arid regions. Salt water and brackish water have long been recognized as potential sources of potable water. Prior art methods of desalination of salt water and/or brackish water include reverse osmosis, evaporation and vapor compression.
In conventional distillation processes, operational costs associated with heating water to produce steam become a key factor in ultimate water cost.
Conventional reverse osmosis systems require pumps to create operational pressures. Reverse osmosis membranes are housed in pressure containers in order to receive the incoming pressurized water. Operational electrical cost for the pumps becomes a key factor in ultimate water cost. Because the cost of creating the pressure is so significant, conventional system connect multiple reverse osmosis elements in series so that brine water from the last element flows as input to the next element. Although any pressure drop across an element is minimal, salt concentration increases because some of the original water has permeated through the last element as product water. As salt concentration for downstream elements due to precipitation of salts increases, scaling of elements increases. Over time, this results in frequent maintenance, that is, cleaning of elements or replacement of elements. Because maintenance cost becomes significant, water pretreatment is done to try to reduce fouling and scaling. The problem, however, is that the cost of pretreatment materials becomes high. All the costs associated with reverse osmosis (electrical, maintenance, pretreatment, element replacement) add together to make the ultimate cost of desalinated water high.
Therefore, there is a continuing need for a method and apparatus for water desalination and/or purification that is efficient, inexpensive and requires infrequent maintenance.
It is an object of the present invention to provide an apparatus and method for desalinating seawater or brine and/or purifying fresh water that contains minerals, salts, and other dissolved solids or pollutants.
It is another object of the present invention to provide an apparatus and method for desalinating seawater or brine and/or purifying fresh water which contains minerals, salts, and other dissolved solids or pollutants which is energy efficient.
It is another object of the present invention to provide an apparatus and method for desalinating seawater or brine and/or purifying fresh water which contains minerals, salts, and other dissolved solids or pollutants, which uses focused solar energy to generate steam.
The apparatus of the present invention is placed in an ocean, lake, or other body of water from which purified water is to be extracted. In one embodiment of the present invention, the apparatus for the desalination or purification of water comprises a non-solid vessel with a bottom defining an opening that is capable of being partially submerged below the surface of a body of water and a pan located within the vessel that is flexibly connected to the inner wall of the vessel and beneath the surface of the water. A lens is fixably connected to the top of the vessel and is focused beneath the surface of the water and above the surface of the pan. Water in the pan is heated, thus producing water vapor as steam. The present invention includes a means for condensing water vapor outside the vessel. In one embodiment, the water vapor is transported to and condensed in a condensation coil below the surface of the water and then pumped to shore. The invention includes a means for varying the orientation of the vessel in accordance with the location of the sun so that the amount of solar energy captured and used in the purification process is maximized. For instance, in one embodiment, a sensing array, which locates the position of the sun, is electrically connected to a controller and a series of trim tanks around the periphery of the vessel. The controller controls the amount of water in the trim tanks such that the vessel and lens are positioned such that the sun""s rays are maintained generally parallel to the focal length of the lens.
The method of the present invention comprises the steps of containing a body of water within a vessel, the vessel having a lens fixably attached at the top and a bottom defining an opening, locating a pan just below the surface of the water, focusing the lens just beneath the surface of the water and just above the bottom surface of the pan 5, condensing water vapor, re-filling the vessel with water as the water is converted to steam, and periodically re-orienting the vessel in a manner that tracks movement of the sun.
The above and other objects, features and advantages of the present invention will be more readily perceived form the following description of the preferred embodiments thereof taken together with the accompanying drawings and claims.